1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member, particularly to an electrophotographic photosensitive member containing an azo pigment having a specified chemical structure.
2. Related Background Art
Known organic photoconductive substances used for electrophotographic photosensitive members include photoconductive polymers typified by poly-N-vinylcarbazole, low-molecular organic photoconductive substances such as 2,5-bis(p-diethylaminophenyl)-1,3,4-oxadiazole, combinations of such organic photoconductive substances with a variety of dyes and pigments, and so forth.
Electrophotographic photosensitive members employing an organic photoconductive substance have advantages that the photoconductive members are producible at high productivity at low cost, and the color sensitivity thereof is arbitrarily controlled by selecting the employed sensitizer such as a dye and a pigment. Therefore, organic photoconductive substances have comprehensively been investigated. Recently, function separation types of photosensitive members have been developed which have a lamination structure comprising a charge-generating layer containing an organic photoconductive dye or pigment and a charge-transporting layer containing aforementioned photoconductive polymer or a low-molecular organic photoconductive substance, whereby the disadvantages of conventional organic electrophotographic photosensitive members such as low sensitivity and low durability have been remarkably alleviated.
Among organic photoconductive substances, generally, azo pigments have superior photoconductivity. Moreover, selection of combinations of an azo component and a coupler component allows control of pigment properties, giving a variety of properties of pigment compounds. Accordingly, many azo pigments have been reported as organic photoconductive substances.
Known couplers for such azo pigments include naphthol AS type compounds as disclosed in Japanese Patent Application Laid-Open No. 47-375438, etc., benzocarbazole compounds as disclosed in Japanese Patent Application Laid-Open No. 53-95033, naphthalimide type compounds as disclosed in Japanese Patent Application Laid-Open No. 54-79632, perylene type compounds as disclosed in Japanese Patent Application Laid-Open No. 57-176055, and so forth.